Helmet



FIG. 1 is a front and right side perspective view of a helmet showing our new design;

FIG. 2 is a front perspective view thereof;

FIG. 3 is a left and bottom perspective view thereof;

FIG. 4 is a rear perspective view thereof;

FIG. 5 is a top perspective view thereof; and,

FIG. 6 is a bottom perspective view thereof, depicting only part of the hose shown in the preceding figures.

The details shown in broken lines form no part of the claimed design. 

The ornamental design for a helmet, as shown and described. 